Perioperative thermal regulation is discussed. A retrospective audit was conducted to identify the incidence and magnitude of hypothermia in abdominal surgical procedures under general anesthesia and to identify variables affecting thermal balance. One hundred and sixteen anesthetic records were reviewed from two major city hospitals. Data collected were length of procedure, temperature change, use of antihypothermia adjuncts, amount of fluids administered, temperature of fluids and gases given, and approximate incision length. Results showed a high incidence of hypothermia (80 percent). The degree of temperature drop was significantly related to incision length (p0.01), length of procedure (p0.05), and blood administered (p,0.02). Heating and humidifying inspired gases was the most successful antihypothermia adjunct to decrease the body temperature drops during these cases (p0.01). The use of a combination of adjuncts is also effective in preventing temperature drops. Suggested guidelines for the prevention of perioperative hypothermia are presented.